[kar]

Dragos,

I did followed through code, but did you read previous posts - the thing is: when I try to declare my own base and derived class with operator= in base class, operator= isn't accessible for object of class deriv if there is no forwarding in deriv class's declaration. Can't see such forwarding in class GeometricBoundaryField (and others) - can you help?

K.

[dmoroian]

Indeed you're right, and it was my mistake. I don't see why in your code it is possible to call int i = 10; d.se(i); but not int i = 10; d.operator=(10); nor int i = 10; d = i;
...promise to look into it!

Dragos

[dmoroian]

Ok, I think I have an answer!
Among other free on-line c++ book, there is also Thinking in C++ by Bruce Eckel. It specifies, and I quote:

Except for the assignment operator, operators are automatically inherited into a derived class.

Which means that, you just picked an unfortunate example, trying to overload operator=. If instead of operator=, you would have chosen any other operator, like operator[], then everything would go smoothly.

I've just tried it, and it works!

I hope this is useful,
Dragos

[kar]

Thank you! I'll take a look at that book

[kar]

Hmm, may I ask about virtual functions and inheritance?

#include <iostream>

using namespace std;

class base1
{
public:
bool use(bool y) {return x(y);}
virtual bool x(bool y) = 0;
};

class base2
{
public:
bool x(bool y) {return !y;}
};

class deriv:
public base1, public base2
{
// whatever
};

int main( int c, char ** a)
{
deriv d;
if (!d.use(1)) cout << "yes";
return 1;
}

But it is "no", because compiler output is:

virtinh.cpp: In function 'int main(int, char**)':
virtinh.cpp:26: error: cannot declare variable 'd' to be of abstract type 'deriv'
virtinh.cpp:20: note: because the following virtual functions are pure within 'deriv':
virtinh.cpp:9: note: virtual bool base1::x(bool)

So is it impossible to "merge" an abstract class with definitions of virtual functions, that reside in another base class similarly to example below?

[su_junwei]

may be the pure virtual function "virtual bool x(bool y) = 0; " in class "base1" should be defined definitely.
Su Junwei

[kar]

That is a whole point of my question, that virtual bool x(bool y) = 0; and I want it to be called from use(..) through deriv d!